Species composition of the biospere


  • Intricate webs of interacting organisms
    • 2,000,000 species are known
    • 18,000 plants & animals discovered per year
    • estimated 87% of Eukaryotas unknown


  • Current composition reflects billions of ways organisms have adapted, over and over, to a changing planet


  • Humans have altered 75% of ice-free surface
    • alters species composition

“Essay of the geography of plants” by Humboldt, 1817

Uneven distribution of plants….

Species are spatially arranged

Species are spatially arranged

Similar biological communities reside within our biomes

Climate drives broad distribution of terrestrial biomes

Biomes have distinct soil types

Species distribution varies widely within biomes

Seasons can impact species distributions

Migration can cross many biomes: Birds

Species may also be adapted for seasonal habitats

Niches define the limiting factors for a species

Ecological Niche =

Tolerance Range: Coral Reefs

Ecological niches exist in n-dimensions

Distribution of species within biological communities overlap

Fundamental vs Realized Niche =

Species distributions are related to their realized niche space

Niches often overlap for different species

Ranges versus distribution: Crocodiles

Ranges versus distribution: Crocodiles

Ranges versus distribution: Plants

seed dispersal: gravity, wind, ballistic, water, and by animals

Species distributions: Coconut tree

Biogeography and species ranges: Alfred Wallace 1859

Zoogeographic regions: Wallace